Electro-optical devices, such as semiconductor lasers, have become important commercial components. They are used in a wide variety of applications including the transfer of data to and from optical storage media, in measurement devices, and as transmitters in optical fiber communication systems.
Semiconductor lasers are manufactured on wafers or substrates. The wafers or substrates are significantly larger than the individual semiconductor lasers. Consequently, bars including one-dimensional arrays or other arrays of multiple semiconductor lasers can be manufactured simultaneously, cleaved or separated from the wafer or substrate and packaged together to produce assemblies with multiple lasers. Due to the manufacturing costs associated with packaging multiple laser assemblies, it is desirable to ensure that each of the semiconductor lasers forming the bar or array within the final assembly are suitable for the desired application. One proven approach to determine suitability is to use a laser bar testing system to characterize operating characteristics of the individual semiconductor lasers forming the bar under test. The bars that do not meet specifications will generally be scrapped before entering into the packaging stage of the manufacturing process. In a conventional laser bar tester, a holder or chuck is removed so that a probe can contact appropriate electrical connections to energize the semiconductor laser under test and to permit an optical sensor to be arranged to intersect the emitted light.
In contrast with conventional bar testers which must accurately apply one or more probes to various electrical contacts and appropriately locate an optical sensor in registration with the optical path of a select laser device on the bar, test solutions for packaged modules or completed assemblies face additional alignment and other environmental issues.
Consider a device under test (DUT) that includes an optical emitter surrounded by a housing. The housing provides for electrical connections (e.g., power and data signal connections) through the base or bottom surface for electrical and physical mounting to a printed circuit board and an optical connection along another surface. The housing of the DUT includes thermally conductive structures for controlling the operating temperature of the optical emitters and any associated electronic circuitry in the package.
To test the device under test across a range of expected operating conditions, it may be desirable to provide accurate temperature control of the DUT while also aligning an optical pickup apparatus with the optical emitter. Manufacturing tolerances and variation of the thermally conductive structures and/or optical emitting surface of the DUT make it problematic to design a test adapter that can controllably and repeatedly align an optical pickup with the optical emitter while also effectively thermally coupling one or both of the thermally conductive structures of the DUT.